Fatty acids, C14-18 and C16-18-unsatd., barium salts

Endpoint summary

Description of key information

Bioaccumulation potential is not relevant since  fatty acids, C14-18 + C16-18, unsatd. are natural fatty acids produced from animal and vegetable fats, which are part of the typical European diet. Long-chain carboxylic acids are readily absorbed as micelle aggregates, esterified with glycerol in chylomicrons and very low density lipoproteins, and transported  via the lymphatic system.  fatty acids, C14-18 + C16-18, unsatd. can either be stored in the form of triglycerides (98% of which occurs in adipose tissue depots) or they can be oxidised for energy via the β-oxidation and tricarboxylic acid cycle pathways of catabolism.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Additional information

Information taken from HERA (2002):

Fatty acids and their salts

Fatty acids are an endogenous part of every living cell and are an essential dietary requirement. They are absorbed, digested, and transported in animals and humans. Proposed mechanisms for fatty acid uptake by different tissues range from passive diffusion to facilitated diffusion or a combination of both (Abumrad et al. 1984; Harris et al., 1980). Radioactivity from labelled fatty acids administered orally, intravenously, intraperitoneally, and intraduodenally has been found in various tissues and in blood and lymph (CIR, 1987).

Fatty acids taken up by the tissues can either be stored in the form of triglycerides (98% of which occurs in adipose tissue depots) or they can be oxidised for energy via the β-oxidation and tricarboxylic acid cycle pathways of catabolism (Masoro, 1977). The β-oxidation of fatty acids occurs in most vertebrate tissues utilising an enzyme complex for the series of oxidation and hydration reactions resulting in the cleavage of acetate groups as acetyl CoA. β-oxidation essentially reduces the alkyl chain length by 2 carbon atoms with the release of acetic acid. This leaves another carboxyl group on the shortened alkyl chain for subsequent further β-oxidation. An additional isomerisation reaction is required for the complete catabolism of oleic acid. Alternate oxidation pathways can be found in the liver (ω-oxidation) and the brain (α-oxidation) (CIR, 1987).

Long chain, saturated fatty acids are less readily absorbed than unsaturated or short chain acids. Stearic acid is the most poorly absorbed of the common fatty acids (Clayton & Clayton, 1982; Opdyke, 1979). Several investigators have also found increasing fatty acid chain length slightly decreased their digestibility (CIR, 1987).

Howes (1975) examined the turnover of [14C] surfactants in the rat and found that at 6h after administration, the C10 and C12 soaps were readily metabolised and the main route of excretion was as 14CO2. The C14 soap was readily incorporated into the body and the 14C excretion was slow. The C16 and C18 soaps showed some metabolism with subsequent 14CO2 excretion but most of the 14C was recovered in the carcass at 6 hours.

Dermal Penetration

It has been shown that the greatest skin penetration of the human epidermis was with C10 and C12 soaps and the rate of percutaneous absorption of sodium laurate is greater than that of most other anionic surfactants. (Prottey and Ferguson, 1975; Madsen et al., 2001; Howes, 1975).

Howes (1975) studied the percutaneous absorption of some anionic surfactants and showed that sodium decanoate was reportedly poorly absorbed through the skin of rats when in uncovered contact for 15 minutes. Penetration through excised human skin proceeded at a rate similar to that for excised rat skin for up to 6 hours; thereafter absorption through human skin was slightly quicker. Also, for the three soaps which penetrated the skin (C10, C12 and C14) there was a lag time of 1 hour before any measurable penetration occurred, but after this the rate of penetration steadily increased. Howes also calculated from human epidermal studies in vitro that only small amounts of the C10, C12 and C14 soaps would be likely to penetrate the skin from a 15 minute wash and rinse in vivo. The low penetration rates of the C16 and C18 soaps suggests that little or none of these would penetrate from a 15 minute wash and rinse in vivo.